Release-13 LTE deployments in unlicensed spectrum will be licensed assisted (also called Licensed Assisted Access-Long Term Evolution or LAA-LTE), which implies that transmission over unlicensed secondary carriers will be anchored to a primary licensed carrier using Release-12 Carrier Aggregation principles. Unlike an IEEE 802.11 wireless local area network (i.e., Wi-Fi® network) in which devices first monitor the medium to detect energy prior to transmission via a Clear Channel Assessment (CCA) procedure, the current Long Term Evolution (LAA-LTE) wireless communication standard does not require an LAA-LTE transmitter to first monitor the medium for energy prior to transmission.
In unlicensed/shared spectrum, particularly in densely deployed scenarios, LAA-LTE Access Point/User Equipment (AP/UE) devices potentially experience interference from other radio access technologies in the same frequency channel (e.g. Wi-Fi, Bluetooth® etc.). Inter-operator interference becomes an issue since an AP and UE belonging to different operators can transmit/receive in the same frequency channels.
Due to lack of Listen-before-Talk (LBT) capability in LAA-LTE, LAA-LTE transmissions from one operator can create high interference levels for LAA-LTE devices belonging to a different operator. LAA-LTE transmissions can also create high levels of interference to Wi-Fi stations (STAs) in the same frequency channels.
Therefore, in the unlicensed spectrum the end-to-end LAA-LTE performance can be significantly impacted by interference from neighbor Wi-Fi devices and LAA-LTE devices from a different operator. This can lead to potential hidden node scenarios where transmissions from the intended LAA-LTE transmitting device and from a neighbor Wi-Fi/LAA-LTE device can collide at an LAA-LTE receiver at almost equal power causing degraded Signal-to-Noise Plus Interference-Ratio (SINR) and possibly failed reception.